In a compression refrigerating machine such as an air conditioning apparatus or a car air conditioner, a chlorofluorocarbon (CFC), a hydrochlorofluorocarbon (HCFC), or the like has been mainly used heretofore. However, such compounds each contain chlorine that is responsible for environmental issues, and hence investigation has been conducted on a chlorine-free alternative refrigerant such as a hydrofluorocarbon (HFC).
A hydrofluorocarbon typified by, for example, 1,1,1,2-tetrafluoroethane, difluoromethane, pentafluoroethane, or 1,1,1-trifluoroethane (hereinafter referred to as “R134a”, “R32”, “R125”, or “R143a”, respectively) has been attracting attention, and, for example, R134a has been used in a car air conditioner system.
However, it has been recently pointed out that R143a also has a high global warming potential, or GWP, and hence so-called natural refrigerants such as carbon dioxide have attracted attention as additional alternative refrigerants from the viewpoint of environmental protection. However, carbon dioxide requires high pressure, and hence cannot be used in the current car air conditioner system.
A refrigerant having a specific polar structure in the molecule such as an unsaturated fluorinated hydrocarbon compound (see, for example, Patent Literature 1), a fluorinated ether compound (see, for example, Patent Literature 2), a fluorinated alcohol compound, or a fluorinated ketone compound has been found to be a refrigerant that has a low global warming potential and can be used in the current car air conditioner system.
However, the fact that replacement with the refrigerant such as the unsaturated fluorinated hydrocarbon compound, the fluorinated ether compound, the fluorinated alcohol compound, or the fluorinated ketone compound worsens abrasion at a sliding part has been perceived as a problem.